This workshop is designed to foster interactions between leaders in the field of skin cell biology and researchers with a background in other fields, especially molecular biology and genetics, and interested in applying their knowledge to complex biological systems such as control of epithelial tissue homeostasis and carcinogenesis. The workshop will consist both of theoretical lectures by leading experts in the field and practical hands-on sessions on the cultivation and use of primary cultures of skin cells of various types. The theoretical lectures will include development of the skin; keratinocyte and melanocyte growth/differentiation control; angiogenesis; mammary gland biology; the immune function of the skin; skin as vehicle for gene therapy. Practical topics will cover culture of primary human and mouse keratinocytes, melanocytes, dermal fibroblasts, endothelial cells, mammary epithelial cells; organotypical cultures; gene transfer techniques and skin reconstitution assays. This workshop was already offered once before, in October 1998, and was very well received. Because of this success, we will maintain the same format for the workshop that we are now proposing. The same list of outstanding scientists that participated as speakers last year have tentatively agreed to again participate this year. They include H. Baden, Harvard; V. Band, New England Medical Center; G. Barsh, Stanford; C. Brisken, Whitehead; R. Burgeson, Harvard; C. Daniel, UCSF; M. Detmar, Harvard; R. Halaban, Yale, T. Kupper, Harvard; N. Parenteau, Organogenesis; J. Parrish, Harvard; J. Rheinwald, Harvard; D. Roop, Baylor; K. Stenn, Johnson and Johnson; J. Sundberg, Jackson Labs; and L. Taichman, SUNY.